How to make a niche out of an object
I would do it this way: Once you've created your sphere, create a mesh with an edge that follow the profile of your excrescence. Once in top view use the Knife Project tool to project the profile on the sphere surface. Now join and delete some vertices, extrude up, close the top, create the small hole, etc... Maybe use the Mirror modifier to duplicate the shape all around, or duplicate this part 3 times, rotate it and paste it all around with the Snap (Vertices mode) + Automatically Merge options activated, and at the end create somme additional edges to sharp the edges.



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